Tapered conductive shield in a &#34;m&#34; type tube to decouple slow and fast modes at the output



United States Patent [54] TAPERED CONDUCTIVE SHIELD IN A M TYPE TUBE TO DECOUPLE SLOW AND FAST MODES ATTHEOUTPUT 2 Claims, 6 Drawing Figs.

[52] U.S.C1. 315/393, 315/35. 315/36; 333/31. 333/91 ,333128 [51] int. Cl. tr ms 4;; H01pl/l6 [50] FieldofSearch 333/31A,

3 l 34, 82A, 81C; 315/35. 3.6, S.38(Original); 331/82 [56] References Cited UNITED STATES PATENTS 2,409,449 10/1946 Sanders.Jr., et al. 333/84(M) 2,542,185 2/1951 FOX 333/22 2,794,143 5/1957 Warnecke et a1 315/39.3X

2,817,040 12/1957 Hull 315/35 2,848,645 8/1958 McBee 315/39.3X 2,948,828 8/1960 Ashkin 3 l5/39.3X 3,221,267 11/1965 Ede et a1. 331/82X 3,377,572 4/1968 Araud 333/31(A) 3,411,034 11/1968 Farney 315/395 FOREIGN PATENTS 755,843 8/1956 Great Britain 333/3l(A) OTHER REFERENCES D. Chen. An Emitting-Sole Linear Magnetron Amplitier, FROM Crossed-Field Microwave Devices," Vol. 2, Ch. 4, Sec. 4.4, pp. 242-443, Academic Press, 1961. TK 787 2 V304 O. Buneman, The RF Theory of Crossed Field Devices, from "Crossed-Field Microwave Devices. Vol. 1, Ch. 5, sec. 5.1.1. pp. 368-373. Academic Press, 1961,TK 7872 V304 Primary Examiner- Herman Karl Saalbach Assistant Examiner--William N. Punter Attorney-Craig, Antonelli, Stewart & Hill ABSTRACT: The coupling between the delay line and the interaction space bounded by the delay line and the sole of a M tube is progressively decreased in the output direction by means of a tapered conductive shield plate located in the vicinity of the output coupling system, so that there is no radiation coupling between the fast :mode energy and the useful slow mode energy propagating on the delay line.

PATENTED DEC 2 2 I976 J- ARA/A00 ATTORNEYS FIG 4 Q FIGS INVENTOR EQZMQQZJ- practically eliminated.

TAPERED CONDUCTIVE SHELD IN A M TYPE TUBETO DECOUPLE SLOW AND FAST MODES AT THE OUTPUT This is a division of application Ser. No. 230,384 filed Oct. 15, 1962, now US. Pat. No. 3,377,572.

The present invention relates to a wave guiding structure, and more particularly to improvements in delay line structures for hyperfrequency M-type tubes.

It is known that certain delay circuits form conduits in which the hyperfrequency energy of a given frequency may propagate simultaneously according to two modes of which the phase velocities are very different, one being the slow or delayed mode, owing to the delay properties of the circuit, and the other being the fast mode of which the phase velocity may be very close to the speed of light. This phenomenon appears particularly in circuits utilized in M-type tubes, that is, in those of which the interaction conduit is limited, in on the one hand, by a geometrically periodic structure and, on the other by a smooth parallel electrode, negative with respect to the potential of the periodic structure and generally referred to as sole. The fast propagation mode is due to this structuralarrangement: namely the periodic structure and the sole behave as two walls of a rectangular waveguide. The electromagnetic energy escapes by radiation from the elements of the delay line and is no longer delayed by it. This is of course a parasitic phenomenon.

This phenomenon also appears more especially in those of the delay circuits of which the periodic structure is of the bartype. Since a coupling exists betweeri the waves of the slow mode and of the fast mode within the regions of the discontinuities of the circuit, a portion of the energy which propagates in the slow mode and which alone is intended to be utilized is transferred to the fast mode which is radiatedby the external circuits as pure loss. It is obvious that this phenomenon, therefore, diminishes the energy output of the tube and is susceptible, in addition thereto, to disturb the proper operation based on the utilization of the slow mode.

The present invention has as'its aimto avoid this inconvenience and to realize delay circuits in which the radiation of energy transferred to the fast mode is strongly diminished or According to the present invention, which relates to a delay circuit susceptible of propagating, at the same time, a slow mode and a fast mode, particularly a circuit for M type amplifier or oscillator tubes comprising a geometrically periodic structure coupled to at least one external circuit, and a sole substantially parallel to this structure, there are provided means to reduce progressively the coupling between the structure and the sole within the region or regions adjacent to the point or points of coupling with the external circuits and going in a direction toward this point or these points.

Different means of realization of this variable coupling may be envisaged, means of which some nonlimitative examples will be described more fully hereinafter.

Accordingly, it is an object of the present invention to provide a delaying structure, particularly for M-type tubes, which avoids the shortcomings of the prior art structures and substantially completely eliminates the disadvantage noted hereinabove.

Another object of the present invention resides in the provision of a delay structure, particularly for M-type tubes, which permits an effective increase in the useful energy output of the tube and at the same time assures proper operation thereof based on the utilization of the desired mode.

Still a further object of the present invention resides in the provision of a delay structure, particularly for M-type tubes, which effectively reduces or practically eliminates the energy radiation due to the transfer of energy to the fast mode.

These and other objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawing which shows, for purposes of illustration only, several embodiments in accordance with the present invention, and wherein:

FIG. I is a longitudinal cross-sectional view of a first embodiment of a delay structure in accordance with the present invention;

FIG. 2 is a plan view of the delay structure shown in FIG. I;

FIG. 3 is a longitudinal cross-sectional view of a second embodiment of a delay structure in accordance with the present invention;

FIG. d is a longitudinal cross-sectional view of a third embodiment of a delay structure in accordance with the present invention, and

FIG. 5 is a longitudinal cross-sectional view of a fourth embodiment of a delay structure in accordance with the present invention.

FIG. 6 is a longitudinal cross-sectional view of a fifth embodiment of a delay structure in accordance with the present invention.

The various figures of the drawing are limited to the schematic illustration of the elements of a hyperfrequency amplifier or oscillator tube essential for the present invention, a tube of which the general structure is well known, per se, as well as the detailed structure of the delay circuits.

Referring now to the drawing wherein like reference numerals are used throughout the various views to designate corresponding parts, and more particularly to FIGS. 1 and 2, reference numeral 1 designates therein the geometrically periodic structure of the'delay circuit, and reference numeral 2 the sole of an M-type amplifier or oscillator tube of which the output is coupled to an external'circuit by a conductor 3. According to the present invention, a plate 4 is disposed in the immediate proximity to the structure I between the latter and the sole 2 and within the region adjacent the coupling 3. FIG. 2, which is a plan view from below,sh0ws that this plate 4 has a tapered shape, for example, a triangular shape, it being understood that the rectilinear sides of the triangle could also be replaced by any other suitable shape, for example, by an exponential shape. This plate 4, which is connected to the potential of the structure 1 operates by decreasing progressively the coupling between the structure 1 and the sole 2, when one moves toward the point of coupling with the external circuit 3. Both theory and tests have shown that the passage of the energy of the fast mode across the coupling 3 is thus strongly diminished, if not completely prevented.

In FIG. 3, in which the same reference numerals again designate the same elements as in the preceding figures, and in which there has beentaken one particular example of construction of the structure I by alternation of bars 5 and baffles or vanes 6 fixed to the back plate 7, the means of reducing the coupling between the periodic structure and the sole in accordance with the present invention consists in disposing the bars 5 more and more deeply in the channels 8 formed between baffles 6 as oneapproaches the coupling 3.

In the embodiment illustrated in FIG. 4, an equivalent means consists of increasing progressively the height of the baffles 6 in the terminal portion of the circuit, when moving in the direction toward the coupling 3, the bars 5 being in this case disposed at the same depth within the channels 8.

In the embodiment illustrated in FIG. 5, another equivalent means consists in more and more closing off the channels 8 when moving in the direction toward the coupling 3, particularly by securing to the baffles 6 shields 9 provided with slots 10 more and more narrow in the direction toward the coupling 3. The depth of the arrangement of the bars 5 and the height of the baffles 6 may then remain constant, though it is also understood that combinations with the structures of the preceding figures can also be envisaged.

The operation and the effect of each of the devices illustrated in FIGS. 3 to 5 is the same as that of FIGS. l and 2 explained hereinabove.

The arrangements described hereinabove may be applied to one or both extremities of the delay circuit of an M-type tube, depending on the particular needs. Even though the coupling 3 has been considered in the descriptive text hereinabove as the output of an amplifier or oscillator, the arrangements according to the present invention may also be applied to the input side of an amplifier if the needtherefor exists. Additionally, the arrangements according to the present invention are applicable not only to unidirncnsional delay circuits, but also to bidimensional circuits without departing from the spirit and scope of the present invention.

While I have shown and described several embodimenm in accordance with the present invention, it is understood that the same is not limited thereto, but is susceptible of many changes and modifications within the spirit and scope thereof, as known to a person skilled in the art. The several means described hereina'oove for varying the coupling between the periodic structure and the external circuit are obviously not limitative of the present invention but admit an numerous equivalent ways as known to a person skilled in the art.

Thus, while I have shown and described several embodiments in accordance with the present invention it is obvious that the same is not limited thereto, but is susceptible of numerous changes and modifications within the spirit and scope thereof, and I therefore do not wish to be limited to the particular details shown and described hereinabove, but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims.

lclaim:

1. In an M-type microwave tube having a delay circuit provided with a geometrically periodical structure, coupling means between at least one predetermined point of said delay circuit and an external circuit, and a sole electrode located in coupled relationship with said delay circuit and being substantially devoid of delaying properties for microwave energy propagating through the tube, the improvement essentially consisting of:

progressive uncoupling means between said delay circuit and said sole electrode, said ,meansextcnding substantially within an area close to said coupling point and being increasingly effective in a direction approaching said point, and v said uncoupling means including tapered plate means so placed as to shield said delay circuit from said sole electrode within the area close to said coupling point.

2. in an M-type microwave tube having a delay circuit provided with a geometrically periodical structure, coupling means between at least one predetermined point of said delay circuit and an external circuit, and a sole electrode located in coupled relationship with said delay circuit and being substantially devoid of delaying properties for microwave energy propagating through the tube, the improvement essentially consisting of:

progressive uncoupling means between said delay circuit and said sole electrode, said means extending substantially within an area close to said coupling point and being increasingly effective in a direction approaching said point;

said uncoupling means including tapered plate means so places as to shield said delay circuit from said sole electrode within the area close to said coupling point; and

said plate being substantially at the potential of said delay circuit. 

